1. Technical Field
The present invention relates to a projector that allows correction of a lens shift.
2. Related Art
It has been known that a projector has functions of lens shifting and trapezoidal distortion correction (hereinafter referred to as distortion correction) for adjusting the position and shape of a projected image projected on a screen or any other projection surface. For example, when the screen is not installed in front of the projector, a lens is shifted in lens shift operation to move the position of the projected image horizontally or vertically. When part of the projected image is still outside the screen, a projector body is so inclined that the entire projected image falls within the screen. In the state in which the projector body is inclined and the projected image falls within the screen, since the shape of the projected image is trapezoidally distorted, distortion correction is so applied that the projected image has a rectangular shape.
In the distortion correction performed by lens shifting operation, it has been known that the effect of the correction changes with the position of the shifted lens. JP-A-2008-236503 describes a projector that incorporates a motorized lens shift mechanism that performs lens shift operation to correct distortion of a projected image appropriately on a detected lens position basis.
The motorized lens shift mechanism incorporated in the projector described in JP-A-2008-236503, however, has a complicated configuration including an electric circuit, resulting in increases in parts cost and manufacturing cost and further resulting in an increase in the weight of the product. It has therefore been difficult to incorporate such a motorized lens shift mechanism in a home-use projector in a medium-to-low price range used in typical households. On the other hand, in a typical household application or other similar types of application, the installation position of a projector and the projection position are both restricted, and the projection position cannot be in front of the installation position in many cases, resulting a high demand for a lens shift mechanism. In these circumstances, a home-use projector employs a manually operated lens shift mechanism that can be incorporated at a low price. The manual lens shift mechanism, which cannot detect the position of a shifted lens, however, cannot appropriately correct distortion on a lens position basis.